Ever make a plane reservation well in advance, try to pick a seat on-line (which the airline suggests that you do), and find out that the only "free" seats are a few crappy middle seats? All the others are "grayed out," indicating that they have already been reserved. Hmm. That's funny, I just bought that ticket, and the plane doesn't leave for a month. Oh, I see, not all the seats are grayed out. There are a few "premium" seats available if I want to fork over some more money. Double hmm. And, did you ever check back shortly before the flight and find that, magically, a few decent seats have opened back up? Triple hmm. Maybe they are just trying to get my money by pretending that seats are taken when they really aren't. Read David Lazarus's article on the topic, which focuses on the shenanigans of American Airlines.